Cardarine was great for the first few months, and then it just completely lost effectiveness for me. I kept trying to get back the effect but had no luck. Maybe I started getting bunk Cardarine from the sources I used? I tried different ones and had no return of benefits. Beyond that, ITPP was fucking awesome, but due to the ban on one of the components to manufacture in China, you (or at least I) cannot find it anymore. GW-0742 has been touted as a Super-Cardarine, and I actually have a bottle of it I have not yet tried.
As far as sides from Cardarine, I never noticed anything other than results until even those faded.